timing four-stroke 50cc scooter

Can you turn the engine over very slowly and still get a spark? You may not be able to if it's a simple magneto but if you can, then setting the timing to a few degrees advanced ought to be good enough to get it running.

A simple way to do this is to take the spark plug out, attach it to the HT lead and rest the plug body against the engine somewhere, rotate the engine slowly until you know it's on the compression stroke ( a finger over the plug hole will feel the compression), back it off a little then put a metal rod (coathanger?) down the hole to meet the top of the piston. Now rotate the engine in the normal direction so the piston rises; the rod will tell you when the piston is at the top of the compression stroke. Your spark should occur just before the piston is at the top. If it doesn't then alter the timing till it does. It may be worth making a pair of marks on the crank pulley/engine case with that rod at its maximum height (TDC) while your doing this, so that you can find TDC more easily in future. .

You'll have to make degree marks on the engine case next to the crank pulley to get an exact timing, I would suggest something like 5 degrees advanced to get it running unless someone knows more specific information.

Hi there,

I am sorry to botter you again but I need some more help. It sruck me, after trying to implement what you said, that I do not know how to alter the timing. In other words, I do not know how to adjust the parts, and which parts. Can you please give me some more info about the matter?

Thank you, Regards

SteveB wrote:

My bike experience is a bit out of date, magnetos used to have a set of points inside them that could be swivelled to adjust the timing. If it's electronic then there must be a pickup sensor doing the same job, perhaps that can be moved. The timing may not be adjustable at all with an electronic system though, but you could still check that it's approximately right the way I described.